Several applications in medicine, biochemistry or chemical engineering require the handling of small precise amounts of liquids. Blood or rare substances have to be analyzed or processed in ever shorter times. Disposable bio chips called LOC (Lab on a chip), μTAS (micro Total Analysis Systems) or DNA micro arrays devices are mostly the key element of a fast and reliable analysis. The exact control of the process liquids is vital for the whole process. Two main methods are usual to achieve high dosage accuracy. It must be also subdivided between internal or external control or generation. The first common used method is to use pumps that deliver the necessary amount directly. Syringe pumps or small gear pumps are reliable and widely accepted external solutions. For on chip pressure generation solutions like electroosmosis (Morf et al., Sensors and Actuators B: Chemical, vol. 72(3), pp. 266-272, 2001), (Guenat et al., Sensors and Actuators B: Chemical, vol. 72(3), pp. 273-282, 2001), applying of static pressure on internal membrane reservoirs (Tamanaha et al., Journal of Micromechanics and Microengineering, vol. 12(2), N7, 2002), thermally created gas bubbles (Handique et al., Analytical Chemistry, vol. 73(8), pp. 1831-1838, 2001), (Zahn et al., Micro Electro Mechanical Systems, The 14th IEEE International Conference on, pp. 503-506, 25-25 Jan. 2001) or the “Lab Disc” approach (Lee et al., Lab on a Chip, vol. 11(1), pp. 70-78, 2011), (Zengerle et al., SELECTBIO 2015 Lab-on-a-Chip Broadcast Event, 16.06.2015) can be found. The second main method is the control of the delivered volumes by using micro valves, which can be on (Ohori et al., Sensors and Actuators A: Physical, vol. 64(1), pp. 57-62, 1998), (Melin et al., Annual Review of Biophysics and Biomolecular Structure, vol. 36(1), pp. 213-231, 2007) or off chip (Bürkert, Buerkert Product overview 05 MicroFluidics, Ingelfingen, 2010). Combinations of both methods can also be found and an implementation of flow sensors is possible.
A thorough cleaning of the devices Is of great importance in order to prevent contaminations. The step of changing the main components is often time intensive but better solutions exist for valves and pumps (Loth et al., Nano/Micro Engineered and Molecular Systems (NEMS), IEEE 10th International Conference on, pp. 9-14, 7-11 Apr. 2015).
With regard to pumps, a major problem for modular systems or small size applications is the large size of external components. They often have a great Internal or dead volume that prevents the integration into small complex systems with high density like e.g. micro fluidic chips. An on-chip pressure generation cannot often be achieved by scaling down conventional macroscopic pumping principles, because of manufacturing, fluid dynamical or material problems in combination with decontamination and costs. In some cases scaling is possible if modifications are carried out, as will be presented.